Need Serious Help With Brand New Sub

Bought a MTX 8000 series 12 and recieved it today. I have 2 of them, hooked up to a JBL 1200.1. One of the subs sound fine, but the other one sounds like crap, it distorts bad, even at low volume levels. I have no idea what is wrong with it. It sounds like the cone is being held down, it makes a bad vibrating noise.

I'll try that, but I just went outside and pressed down on the middle, cuz I could feel air blowing out. and I held it down and the vibration stopped, so I think the dust cap may be loose, not glued well. I'm thinking about going to Circuit City, buying a new one, then taking this one back and getting my money back, I just hope they still carry the 8000's

I switched the 8000's out with the one I bought at CC then took it back. Hope I dont get caught. This new one is not as clean as the other one either. But I had them aimed up toward the glass of my hatchback. I aimed them toward the trunk and its alot cleaner, it hits pretty hard but not as hard as I hoped. Maybe I'm just used to Subs to the point that they arent that loud to me anymore, but 2 MTX 8000 12's and a JBL 1200.1 ?? should be loud right? It barely hurts my ears at high volumes, I was expecting my ear drums to itch.